This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 11-139675, filed May 20, 1999; No. 11-139676, filed May 20, 1999; No. 11-139681, filed May 20, 1999; and No. 11-139682, filed May 20, 1999, the entire contents of which are incorporated herein by reference.
This invention relates to a distance-measuring system used in an image pickup device, such as a silver bromide camera, a digital camera, or a video camera, and more particularly to a distance-measuring system for measuring subject distances at points on the shooting screen (so-called multi-autofocus, hereinafter referred to as multi-AF), characterized by a wide distance-measuring area, such as full-screen AF.
Today, it is becoming quite common for image pickup devices, such as cameras, to implement multi-AF. Cameras equipped with a distance-measuring device for measuring subject distances at three, five, or seven points on the shooting screen are commercially available in low-price models.
The multi-AF is one-dimensional multi-AF where distance-measuring areas are arranged on a straight line. Recently, there have been signs of the commercialization of two-dimensional multi-AF or area AF.
For example, a camera equipped with a distance-measuring device having an area AF function using as many as 45 distance-measuring areas 17 on the finder view 16 has been commercialized and put on the market.
In such conventional multi-AF, complex calculations, such as distance-measuring calculations, must be repeated as many times as the number of distance-measuring areas increases. To improve the time-lag, various inventions have been disclosed.
For example, Jpn. Pat. Appln. KOKAI Publication No. 2-158705 has disclosed the technique for acquiring pieces of subject distance information in a first distance-measuring mode in which the distances to points on the subjects are measured roughly, selecting the subject presenting the shortest distance, and measuring the distance only to the selected subject with high accuracy in a second distance-measuring mode, thereby improving the time-lag.
Furthermore, Jpn. Pat. Appln. KOKAI Publication No. 63-131019 has disclosed a technique which is based on the assumption that, in active AF, the closest main subject is present at the place where the amount of light reflected from the projected light is the greatest and which omits distance-measuring calculations for parts where the amount of reflected light is small, thereby improving the time-lag.
Since all the conventional AF methods have used active AF, they have improved the time-lag remarkably. When they attempt to perform full-screen AF or the like, however, a set of light projecting elements and a set of light-receiving elements cannot avoid becoming very large, which is an obstacle to putting the device to practical use.
In contrast, passive AF would miniaturize the light-receiving elements much more than active AF, causing no obstacle to putting the device to practical use. Thus, passive AF is more suitable for wide-range multi-AF, such as full-screen AF, than active AF.
In this connection, Jpn. Pat. Appln. KOKAI Publication No. 62-103615 has disclosed the technique for performing rough correlation operation on distance-measuring areas, selecting one of the distance-measuring areas on the basis of the result of the operation, and then performing high-accuracy correlation operation on only the selected distance-measuring area, thereby improving the time lag by passive AF.
The rough correlation operation is performed by thinning out sensor data items, such as using every other sensor data item in calculations, but can never be omitted. Thus, although active AF has a higher efficiency of time-lag measures than passive AF, both types of AF produce the same effect.
A recently proposed solution to the problem of which of passive AF and active AF is-more suitable for wide-range multi-AF, such as full-screen AF, is a distance-measuring method using/hybrid AF. In hybrid AF, which is now in use, a steady-state light removing circuit for removing steady-state light is provided for each light-receiving element in a passive sensor. A passive operation is performed, when the steady-state light removing function is disabled, whereas an active operation is performed when the steady-state light removing function is enabled. Jpn. Pat. Appln. KOKAI Publication No. 10-336921 has disclosed such a steady-state light removing circuit. Products using hybrid AF are already available on the market.
To perform wide-range multi-AF, such as full-screen AF, time-lag measures are essential. For this reason, various devices have been thought out to avoid using high-speed, expensive CPUs and microcomputers at the sacrifice of cost. One of principal devices divides the process of measuring the distance in two: the first half of the process for pre-distance measurement and the second half of the process for actual distance measurement.
The purpose of the pre-distance measurement is to measure the distance roughly in a short time and estimate the position of the main subject, whereas the purpose of the actual distance measurement is to limit time-consuming high-accuracy distance measurement to the necessary-minimum subjects on the basis of the result of the pre-distance measurement in the preceding process. Although the process of short-time pre-distance measurement increases, the time required to measure the distances to the subjects excluded is eliminated, which helps shorten the entire distance-measuring time.
More specifically, in one type of pre-distance measurement, light is projected onto subjects and the position of the main subject is estimated on the basis of the amount of reflected light.
In the estimating method, the subject with the largest amount of reflected light is generally judged to be the main subject present at the shortest distance.
The estimating method, however, can make a wrong estimate of the position of the main subject because of the effect of the reflectivity of the subject.
Therefore, when wide-range multi-AF, such as full-screen AF, is effected in the prior art, the problem is how to deal with the reflectivity of the subject.
In the estimating method, if lustrous things, such as glass, were included in the subjects, the main subject might be estimated erroneously because of the regular reflection of the lustrous things.
Thus, when wide-range multi-AF, such as full-screen AF, is effected in the prior art, the problem is how to deal with lustrous things, such as glass.
In addition, if integration control is not best suited for the main subject in producing an image signal of the subjects even when the position of the main subject has been determined, especially if a highly luminous thing is included in the distance-measuring range, the image signal of the main subject can be corrupted and distance measurement therefore be impossible. This is a drawback in the prior art. Thus, the problem is how to deal with highly luminous things.
Furthermore, an attempt to effect wide-range AF, such as full-screen AF, requires measures to cope with time-lag. Up to now, however, there has been no conventional device which has included an effective distance-measuring system and taken measures against time-lag.
Specifically, in the prior art, measures have been taken against time-lag only by using expensive, fast CPUs or microcomputers at the sacrifice of cost.
Therefore, the prior-art distance-measuring device has a disadvantage in that it has taken insufficient measures against time-lag and therefore has had great time-lag.
An object of the present invention is to provide a high-accuracy distance-measuring system which estimates the position of the main subject correctly without being affected by the reflectivity of subjects, operates at higher speed with less time-lag, assures a high reliability of the result of distance measurement, and suppresses a rise in manufacturing cost.
Another object of the present invention is to provide a high-accuracy distance-measuring system which estimates the position of the main subject correctly without being affected by lustrous objects, such as glass, operates at higher speed with less time-lag, assures a high reliability of the result of distance measurement, and suppresses a rise in manufacturing cost.
Still another object of the present invention is to provide a high-accuracy distance-measuring system which is unaffected by highly luminous things included in the subjects and suppresses a rise in manufacturing cost.
Still another object of the present invention is to provide a distance-measuring system which operates at higher speed with less time-lag, provides a highly reliable result of distance measurement with high accuracy, and suppresses a rise in manufacturing cost.
To accomplish the foregoing objects, a distance-measuring device according to a first aspect of the present invention comprises: at least a pair of integration-type light-receiving sensors for receiving the light from subjects and producing a subject image signal; a light projecting section for projecting light onto subjects; a steady-state light removing section for obtaining an image signal by removing the steady-state light component from the subject image signal the pair of integration-type light-receiving sensors produces, while the light projecting section is projecting light onto the subjects; a first distance-measuring section for measuring a subject distance on the basis of the image signal obtained by causing the steady-state light removing section to remove the steady-state light component from the subject image signal; a subject select section for causing the first distance-measuring section to make distance measurements for a specific time and, on the basis of the resulting image signal, selecting a subject with an integrated value in a specific range determined by the reflectivity of the subjects from the largest integrated value excluding the high-frequency peak as a subject whose distance is to be measured; and a second distance-measuring section for measuring the distance to the subject whose distance is to be measured which has been selected by the subject select section, on the basis of the subject image signal obtained by the pair of integration-type light-receiving sensors, while the light projecting section is not projecting light onto the subjects.
To accomplish the foregoing objects, a distance-measuring device according to a second aspect of the present invention comprises: at least a pair of integration-type light-receiving sensors for receiving the light from subjects and producing a subject image signal; a light projecting section for projecting light onto subjects; a steady-state light removing section for obtaining an image signal by removing the steady-state light component from the subject image signal the pair of integration-type light-receiving sensors produces, while the light projecting section is projecting light onto the subjects; a first distance-measuring section for measuring a subject distance on the basis of the image signal obtained by causing the steady-state light removing section to remove the steady-state light component from the subject image signal; a subject select section for causing the first distance-measuring section to make distance measurements for a specific time, setting a sensing area where the main subject is present on the basis of the result of integration of the resulting reflected signal component, and selecting a subject whose distance is to be measured on the basis of the extreme value of the result of integration over the set area by the integration-type light-receiving sensors; and a second distance-measuring section for measuring the distance to the subject whose distance is to be measured which has been selected by the subject select section, on the basis of the subject image signal obtained by the pair of integration-type light-receiving sensors, while the light projecting section is not projecting light onto the subjects.
To accomplish the foregoing objects, a distance-measuring device according to a third aspect of the present invention comprises: at least a pair of integration-type light-receiving sensors for receiving the light from subjects and producing a subject image signal; a light projecting section for projecting light onto subjects; a steady-state light removing section for obtaining an image signal by removing the steady-state light component from the subject image signal the pair of integration-type light-receiving sensors produces, while the light projecting section is projecting light onto the subjects; a first distance-measuring section for measuring a subject distance on the basis of the image signal obtained by causing the steady-state light removing section to remove the steady-state light component from the subject image signal; a distance-measuring area setting section for causing the first distance-measuring section to make distance measurements for a specific time, sensing the peak value of the resulting image signal and its position on the sensors, and setting a distance-measuring area including the main subject on the basis of the results of the sensing; and a second distance-measuring section for measuring the distance to a subject in the distance-measuring area set by the distance-measuring area setting section, on the basis of the subject image signal obtained by the pair of integration-type light-receiving sensors, while the light projecting section is not projecting light onto the subjects.
To accomplish the foregoing objects, a distance-measuring device according to a fourth aspect of the present invention comprises: at least a pair of integration-type light-receiving sensors for receiving the light from subjects and producing a subject image signal; a light projecting section for projecting light onto subjects; a steady-state light removing section for obtaining an image signal by removing the steady-state light component from the subject image signal the pair of integration-type light-receiving sensors produces, while the light projecting section is projecting light onto the subjects; a first distance-measuring section for measuring a subject distance on the basis of the image signal obtained by causing the steady-state light removing section to remove the steady-state light component from the subject image signal; a subject select section for causing the first distance-measuring section to make distance measurements for a specific time and, on the basis of the resulting image signal, selecting a subject whose distance is to be measured from the subjects with integrated values in a specific range; and a second distance-measuring section for measuring the distance to the subject whose distance is to be measured which has been selected by the subject select section, on the basis of the subject image signal obtained by the pair of integration-type light-receiving sensors, while the light projecting section is not projecting light onto the subjects.
To accomplish the foregoing objects, a distance-measuring device according to a fifth aspect of the present invention comprises: at least a pair of integration-type light-receiving sensors for receiving the light from subjects and producing a subject image signal; a light projecting section for projecting light onto subjects; a steady-state light removing section for obtaining an image signal by removing the steady-state light component from the subject image signal the pair of integration-type light-receiving sensors produces, while the light projecting section is projecting light onto the subjects; a first distance-measuring section for measuring a subject distance on the basis of the image signal obtained by causing the steady-state light removing section to remove the steady-state light component from the subject image signal; a subject select section for causing the first distance-measuring section to make distance measurements for a specific time and, on the basis of the resulting image signal, selecting a subject whose distance is to be measured from the subjects in a specific spatial frequency range; and a second distance-measuring section for measuring the distance to the subject whose distance is to be measured which has been selected by the subject select section, on the basis of the subject image signal obtained by the pair of integration-type light-receiving sensors, while the light projecting section is not projecting light onto the subjects.
To accomplish the foregoing objects, a distance-measuring device according to a sixth aspect of the present invention comprises: at least a pair of integration-type light-receiving sensors for receiving the light from subjects and producing a subject image signal; a light projecting section for projecting light onto subjects; a steady-state light removing section for obtaining an image signal by removing the steady-state light component from the subject image signal the pair of integration-type light-receiving sensors produces, while the light projecting section is projecting light onto the subjects; a first distance-measuring section for measuring a subject distance on the basis of the image signal obtained by causing the steady-state light removing section to remove the steady-state light component from the subject image signal; a sensing area setting section for causing the first distance-measuring section to make distance measurements for a specific time and setting a sensing area where the main subject is present on the basis of the result of integration of the resulting reflected signal component; and a second distance-measuring section for measuring the subject distance on the basis of the largest integrated value in a specific spatial frequency range of the result of integration by the integration-type sensors for the sensing area set by the sensing area setting section and on the basis of the subject image signal obtained by the pair of integration-type light-receiving sensors, while the light projecting section is not projecting light onto the subjects.
To accomplish the foregoing objects, a distance-measuring device according to a seventh aspect of the present invention comprises: at least a pair of integration-type light-receiving sensors for receiving the light from subjects and producing a subject image signal; a light projecting section for projecting light onto subjects; a steady-state light removing section for obtaining an image signal by removing the steady-state light component from the subject image signal the pair of integration-type light-receiving sensors produces, while the light projecting section is projecting light onto the subjects; a first distance-measuring section for measuring a subject distance on the basis of the image signal obtained by causing the steady-state light removing section to remove the steady-state light component from the subject image signal; a subject estimation and sensing area setting section for causing the first distance-measuring section to make distance measurements for a specific time and, on the basis of the resulting image signal, not only estimating the main subject but also selecting a sensing area for a monitor signal used in integration control in continuing to obtain the subject image signal; and a second distance-measuring section for measuring the distance to the main subject estimated by the subject estimation and sensing area setting section, on the basis of the subject image signal obtained by the pair of integration-type light-receiving sensors, while the light projecting section is not projecting light onto the subjects.
To accomplish the foregoing objects, a distance-measuring device according to an eighth aspect of the present invention comprises: at least a pair of integration-type light-receiving sensors for receiving the light from subjects and producing a subject image signal; a light projecting section for projecting light onto subjects; a steady-state light removing section for obtaining an image signal by removing the steady-state light component from the subject image signal the pair of integration-type light-receiving sensors produces, while the light projecting section is projecting light onto the subjects; a first distance-measuring section for measuring a subject distance on the basis of the image signal obtained by causing the steady-state light removing section to remove the steady-state light component from the subject image signal; a subject estimation and distance-measuring area setting section for causing the first distance-measuring section to make distance measurements for a specific time and, on the basis of the resulting reflected-light image signal, not only estimating the position of the main subject but also setting a sensing area including the estimated position as an area where distance is to be measured; and a second distance-measuring section for measuring the distance to the main subject estimated by the subject estimation and distance-measuring area setting section, on the basis of the subject image signal obtained by the pair of integration-type light-receiving sensors, while the light projecting section is not projecting light onto the subjects.
It is desirable that the estimated position of the main subject should be a position at which the reflected light image signal has the largest integrated value.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.